Solve for $p$ : $18 + p = 11$
Explanation: Subtract $18$ from both sides: $ \begin{eqnarray} \\ 18 + p &=& 11 \\ \\ {-18} && {-18} \end{eqnarray} $ $ \begin{eqnarray} \hphantom{18 + p} &\hphantom{=}& \hphantom{11} \\ p &=& 11 {- 18} \\ \end{eqnarray} $ Simplify. $ p = -7$